Android Jamendo源码 图片缓存实现

Jamendo 代码Image缓存实现：

package com.teleca.jamendo.util;

import java.util.WeakHashMap;

import android.graphics.Bitmap;

/**
 * Caches downloaded images, saves bandwidth and user's
 * packets
 * 
 * @author Lukasz Wisniewski
 */
public class ImageCache extends WeakHashMap<String, Bitmap> {

	//WeakHashMap....add by gjican...
	private static final long serialVersionUID = 1L;
	
	public boolean isCached(String url){
		return containsKey(url) && get(url) != null;
	}

}

   在JamendoApplicatin中定义一个全局的getImageCache()来获得当前应用程序图片缓存  JamendoApplication.getInstance().getImageCache().put(mTaskUrl, bmp);

   然后在每次下载图片之前先进行判断，看是否缓存里存在此图片，若有则直接显示，否则调用DownloadTast()去下载

  

		public String doInBackground(String... params) {

			mTaskUrl = params[0];
			InputStream stream = null;
			URL imageUrl;
			Bitmap bmp = null;

			try {
				imageUrl = new URL(mTaskUrl);
				try {
					stream = imageUrl.openStream();
					bmp = BitmapFactory.decodeStream(stream);
					try {
						if(bmp != null){
							JamendoApplication.getInstance().getImageCache().put(mTaskUrl, bmp);
							Log.d(JamendoApplication.TAG, "Image cached "+mTaskUrl);
						} else {
							Log.w(JamendoApplication.TAG, "Failed to cache "+mTaskUrl);
						}
					} catch (NullPointerException e) {
						Log.w(JamendoApplication.TAG, "Failed to cache "+mTaskUrl);
					}
				} catch (IOException e) {
					Log.w(JamendoApplication.TAG, "Couldn't load bitmap from url: " + mTaskUrl);
				} finally {
					try {
						if(stream != null){
							stream.close();
						}
					} catch (IOException e) {}
				}

			} catch (MalformedURLException e) {
				e.printStackTrace();
			}
			return mTaskUrl;
		}